Salt Coated With Nanoparticles

ABSTRACT

A salt or CaO coated with hydrophobic nanoparticles comprises an inner part and an outer coating, forming a particle with a permeable membrane keeping liquid inside and letting gas pass. Said inner part comprises at least one selected from a salt and CaO and said outer coating comprises hydrophobic nanoparticles. Known machines and processes can get enhanced functionality the particles comprising salt and nanoparticles. For machines working according to matrix and hybrid principles the particles can act as a matrix, thereby substituting expensive matrix material. Further applications include storage of chemical energy. A device is adapted to perform an absorption process, said device comprising at least one particle. Advantages include that corrosion is reduced or even eliminated. The long term stability of absorption machines is increased and migration of salt in liquid and gas phase is avoided.

TECHNICAL FIELD

The present invention relates to a particle comprising an inner part andan outer coating and it also relates to a device comprising a particle.The inner part comprises at least one selected from a salt and CaO andthe outer coating comprises hydrophobic nanoparticles. The device issuitable for performing an absorption process. Examples of such devicesinclude but are not limited to an absorption chemical heat pump.

BACKGROUND

Salts in connection with other substances including silica are known.U.S. Pat. No. 5,753,345 discloses an adsorber for humidity and odorousgas exchange. A silica sol is coated on a sheet to obtain an adsorbingbody. The silica particles have a diameter <120 Å and a plurality ofstable silanol radicals on the surface, giving strong binding ability.The silica sol optionally comprises a humidity absorbing agent such asfor instance lithium salts, magnesium salts and calcium salts. Thesilica sol coating is applied on a sheet or a laminate and dried togelatinize it and is then rigidly fixed on said sheet or laminate.

Tablets of salts together with binders are also known. US 2006/0097223discloses a device for controlling relative humidity with a solidifiedhumectant composition. The solidified humectant composition is made froma humectant salt, water, and a carrier. The solidified humectant may beformed into a tablet with the aid of a binder, or it may be containedwithin a thermoformed felt material, a sachet, or a water permeablecanister. Examples of salts include CaCl₂, K₂CO₃, LiCl₂, NaCl, andK₂SO₄. Examples of carriers include silica gel.

The principle of the operation of chemical heat pumps is well-known, seefor example U.S. Pat. No. 5,440,889, U.S. Pat. No. 5,056,591, U.S. Pat.No. 4,993,239, U.S. Pat. No. 4,754,805 as well as U.S. Pat. No.6,634,183. Many chemical heat pumps comprise at least one salt as anactive substance and at least one liquid. In U.S. Pat. No. 6,634,183there is described a solid phase of an active substance primarilylocated inside a net, while a solution phase is able to pass the net.There is further provided distribution means such as a pump to make theseparated active substance in liquid state or solution phase pass incontact with a heat exchanger and the active substance in solid state.

A drawback relating to the use of salt solutions in absorption processesis that corrosion easily occurs. Corrosion typically results in theformation of non condensable gases, mainly hydrogen gas (H₂), or evenrupture of the building material in a machine working according to theabsorption process. The effects of corrosion gases decrease or stop theabsorption process. A problem in connection with corrosion is thathydrogen gas has to be purged from the system.

In known absorption processes, the problem of corrosion is difficult tosolve since corrosion can only partly be inhibited by for example theaddition of different corrosion inhibitors, adjustment of the pH or bychoosing a corrosion resistant material from the group of noble, andthereby expensive, metals.

US 2002/0043649 describes an effort to control the corrosion in heatpumps by adding a rare earth metal salt to the heat pump's ammonia/waterworking fluid. In preferred embodiments, the rare earth metal saltincludes cerium, and the steel surfaces are cerated to enhance thecorrosion-inhibiting effects.

Although chemical heat pumps working in accordance to the hybridprincipal and involving a matrix are used successfully today, see forexample PCT applications WO 2007/139476 and WO/2009/102271, the longterm stability can still be improved. Sometimes, liquid migration of thesalt inside the matrix may occur over long periods of time. This saltmigration causes an uneven salt concentration in the matrix, resultingin a decreased performance of the machine. Moreover, in such a machine,salt can also migrate in liquid droplets with the gas flow and therebyslowly contaminate the condenser/evaporator. This affects theperformance of the heat pump negatively. Thus, regarding the long termstability there is room for improvement.

Yet another problem with chemical heat pumps working in accordance tothe hybrid principle involving a matrix is that the matrix materialitself may be of a corrosion sensitive material. The corrosion of thematrix may result in general corrosion related problems such as releaseof corrosion gases but it may also result in the degradation of thematrix, an unwanted side effect.

In chemical heat pumps working in accordance to the hybrid principleinvolving a matrix, the gas transport during charging and discharging isreduced by salt water solution blocking the gas channels in the matrix.It is desired to reduce or eliminate this problem.

In chemical heat pumps working in accordance to the hybrid principleinvolving a matrix, the volume of the gas channels in the matrix varydepending on the amount of liquid absorbed in the matrix, this variationmay lead to unwanted effects. It is desired to reduce or even eliminatethis problem.

In chemical heat pumps working in accordance to the hybrid principleinvolving a matrix or working according to principals of falling film itis always beneficial for good performance to have a great surfacecontact between the gas phase and the salt. This is valid both duringcharging and discharging. Thus it is desired to increase the contactarea between a gas phase and a salt in a chemical heat pump workingaccording to the hybrid principle. In the present chemical heat pumpsworking in accordance to the hybrid principle there is room forimprovement regarding the surface area.

“Dry water” is a known material comprising water and hydrophobicnanoparticles. The material is a free flowing powder that is prepared bymixing water, hydrophobic nanoparticles, e.g. silica derivatives such assilica dimethyl silylate, and air at high speeds. The mixing at highspeeds results in a water-in-air emulsion, creating particles where thenanoparticles are arranged enclosing small water droplets, acting as abarrier between the environment and water. The water droplets areseparated and prevented from fusing. The emulsion formed is dry and canbe poured as a free flowing powder. The concept of dry water and how itis made has been known since the 1960's, see for example U.S. Pat. No.3,393,155 and U.S. Pat. No. 4,008,170, however in recent years dry waterhas regained interest. Application areas for dry water have for examplebeen mentioned to be an ingredient in cosmetics, for storage of gases orfor speeding up catalytic reactions. One problem with structures made ofdry water is that they tend to collapse when they are heated so that thewater evaporates. Thus it is difficult to obtain a fully reversibleprocess.

In the prior art there is further a need for an energy carrier which iseasy, simple and economical to transport.

SUMMARY

It is an object of the present invention to obviate at least some of theproblems in the prior art and to provide an improved particle, animproved device and a method for manufacturing the particle.

In a first aspect there is provided a particle comprising an inner partand an outer coating, said inner part comprises at least one selectedfrom a salt and CaO and said outer coating comprises hydrophobicnanoparticles, wherein the particle has an average size from 1 to 1000μm.

In a second aspect there is provided a device adapted to perform anabsorption process, said device comprising a particle, the particlecomprising an inner part and an outer coating, said inner part comprisesat least one selected from a salt and CaO and said outer coatingcomprises hydrophobic nanoparticles, wherein the particle has an averagesize from 1 to 1000 μm.

There is further provided use of the salt and/or CaO coated withnanoparticles in an absorption process.

There is further provided a method for manufacturing a particlecomprising a salt coated with nanoparticles.

Advantages of the invention include that corrosion is reduced or eveneliminated because the corrosive salt is enclosed within thenanoparticles. The long term stability of absorption machines isincreased, since salt and/or CaO is enclosed with nanoparticles, formingparticles of coated salt and/or CaO. An NCS particle refers to aparticle comprising a salt and/or CaO coated with hydrophobicnanoparticles. The forming of a NCS particle stops or essentially stopssalt migration in both gas and liquid phase. During operation togetherwith a volatile liquid, the salt is enclosed within the particle andcannot obstruct the flow of gas between NCS particles.

The surface area is increased due to the small size of the NCSparticles. In one embodiment, a surface contact of 100 times greaterthan in comparable machines in the prior art is achieved by using theNCS particle. The comparable machines in the prior art refers to wellknown machines such as falling film machines and spraying machines.

Another advantage for absorption machines comprising the NCS particle ofthe present invention is that the present NCS particles allow an absenceof expensive circulating pumps and expensive heat exchangers thatcorrode with time and requires permanent service for example to refillpH buffer and corrosion inhibitors and vacuum pumping/purging ofhydrogen gas that is the result of corrosion of a metal.

Yet another advantage of the NCS particles is that in certain aspectsthey behave as a solid and therefore any migration of liquid caused bygravity and/or temperature gradients is stopped and the problem with anuneven salt concentration in a matrix can therefore be overcome. Even ifexposed to humid air, the NCS particles do not migrate or fuse forminglumps but stay as a free flowing powder due to the stable nature of theNCS particle. Moreover, since the salt is enclosed in the NCS particle,the problem of possible corrosion of the matrix material is overcomesince the salt essentially does not come in contact with the matrixmaterial.

The salt coated with nanoparticles offers a new possibility for machinesworking according to matrix and hybrid principles (see for example WO2007/139476 and WO/2009/102271), since the material in itself can act asa matrix, the NCS particle can thereby substitute expensive matrixmaterial. The salt coated with nanoparticles comprises an inner part andan outer coating, forming a particle with a permeable membrane keepingliquid inside and allowing gas to pass in or out. Thus, no additionalmatrix is needed in absorption machines working with a matrix accordingto the hybrid principle.

Still another advantage is that in an absorption machine the channelstructure between the present NCS particles remains constant compared toprior art where the channel structure is a function of liquid contentand results in liquid film formation and process termination despite ofthe possible presence of dry salt in the bulk. The present particlesalso keep essentially the same volume regardless if they are full ofliquid or totally dry and thereby never or essentially never block thegas channels in the matrix. The NCS particle (in one embodiment with asize of 45-100 μm) always gives a 40% free space by laws of geometry.

Yet another advantage is that the salt and/or coated with nanoparticlesis characterized by its ability to fully release its liquid content byinfluence of heat up to a high temperature without collapsing.Subsequently, it can regain the liquid if vapor and cooling isavailable. In one embodiment the NCS particle can be used attemperatures above 400° C. This recycling ability makes, in contrast to“dry water”, new applications possible and enhanced functionality can begiven to known machines and processes. “Dry water” collapses when wateris removed from the structure.

Given the advantages above, it is realized that absorption machines arevery well suited for use with the present NCS particles.

The salt and/or CaO coated with hydrophobic nanoparticles can be easilytransported in plastic bags, paper bags, drums and does not requireexpensive and corrosion resistant plastic/metal containers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described, by way of example, with reference to theaccompanying drawings, in which:

FIG. 1 shows a SEM micrograph of an NCS particle. The particle wasmanufactured from a solution of LiBr in water and coated with silicawhich was polydimethylsiloxy modified.

FIG. 2 shows a schematic drawing of NCS particles with and without watermolecules.

FIG. 3 shows a SEM micrograph of a newly manufactured NCS particle ofCaO(/Ca(OH)2) coated with nanoparticles.

FIG. 4 shows a SEM micrograph of the same NCS particle as in FIG. 3after 1300 cycles.

DETAILED DESCRIPTION

Before the invention is disclosed and described in detail, it is to beunderstood that this invention is not limited to particular compounds,configurations, method steps, substrates, and materials disclosed hereinas such compounds, configurations, method steps, substrates, andmaterials may vary somewhat. It is also to be understood that theterminology employed herein is used for the purpose of describingparticular embodiments only and is not intended to be limiting since thescope of the present invention is limited only by the appended claimsand equivalents thereof.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a”, “an” and “the” include plural referentsunless the context clearly dictates otherwise.

If nothing else is defined, any terms and scientific terminology usedherein are intended to have the meanings commonly understood by those ofskill in the art to which this invention pertains.

The term “about” as used in connection with a numerical value throughoutthe description and the claims denotes an interval of accuracy, familiarand acceptable to a person skilled in the art. Said interval is ±10%.

“Average size” is used in connection with a nanoparticle or a particleto denote the average of the size. The definition is based on replacinga given irregularly shaped particle with an imaginary sphere that hasthe volume identical with the irregularly shaped particle. This volumebased particle size equals the diameter of the sphere that has samevolume as a given irregularly shaped particle.

“Hygroscopic” is used herein to denote the ability of a substance toattract water molecules or molecules with similar properties as waterfrom the surrounding environment through either absorption oradsorption.

“Hydrophobic” is used herein to denote the property of beingwater-repellent, tending to repel and not absorb water.

“Nanoparticle” is used herein to denote a localized object with a volumeand a mass. In particular “nanoparticle” is used to denote particleswhich form the coating of the NCS particle. “Nanoparticles” are thussmaller than the NCS particle.

“NCS particle” is used herein to denote a localized object with a volumeand a mass. In particular “particle” and/or “NCS particle” is used todenote an object comprising a salt which object is coated with verysmall particles called nanoparticles. Thus the word “particle” may referto an object comprising an inner part and an outer coating, wherein theouter coating comprises nanoparticles, which nanoparticles are smallerthan the particle. NCS is an abbreviation of nano coated salt.

“Salt” is used herein to denote a compound formed by interaction ofequivalent amounts of an acid and a base. The term “salt” as used hereinincludes alkaline salts, i.e. salts that hydrolyze to produce hydroxideions when dissolved in water and acid salts, i.e. salts that hydrolyzeto produce hydronium ions in water.

In the present invention a salt and/or CaO is coated with hydrophobicnanoparticles obtaining a NCS particle.

In a first aspect there is provided a particle comprising an inner partand an outer coating, said inner part comprises at least one selectedfrom a salt and CaO and said outer coating comprises nanoparticles,wherein the particle has an average size from 1 to 1000 μm.

It is to be understood that the particle comprises at least one coating.Thus the particle may comprise several coatings. The inner part of theparticle may in turn comprise several different parts.

The inner part comprises at least one selected from a salt and CaO. Inone embodiment the inner part comprises a salt. In one embodiment theinner part comprises CaO. An advantage of CaO is that high temperaturescan be utilized. The skilled person realizes that when CaO is utilizedin a process involving H₂O, also Ca(OH)₂ is in the NCS particles atleast during some conditions, thus also Ca(OH)₂ is encompassed withinthe term CaO.

In general any salt can be used. The salt is an ionic compound. In oneembodiment the salt is in a dry state. In an alternative embodiment thesalt is hydrated, i.e. the salt contains water molecules inside thecrystal lattice. In yet another embodiment the salt is dissolved atleast partially in water.

In one embodiment, the salt is hygroscopic. In one embodiment the saltis selected from chlorides, chlorates, perchlorates, bromides, iodides,carbonates, and nitrates of lithium, magnesium, calcium, strontium,barium, cobalt, nickel, iron, zinc, manganese, potassium, and aluminumas well as sulphides and hydroxides of lithium, sodium and potassium. Inanother embodiment the salt is selected from Na₂S, LiBr, LiCl, CaCl₂,and CaBr₂. In one embodiment the salt is selected from magnesiumchloride, zinc chloride, potassium carbonate, potassium hydroxide andsodium hydroxide. Where existing, all hydrated versions of all abovesalts are also encompassed. As a non limiting example Na₂S*9H₂O isencompassed.

The nanoparticles are hydrophobic. In one embodiment the nanoparticlescomprise at least one material selected from hydrophobically modifiedSiO₂ particles and carbon materials. In one embodiment the nanoparticlescomprise hydrophobically modified silica particles. Hydrophobicallymodified SiO₂ particles encompass particles comprising SiO₂ and whichhave been modified to obtain hydrophobic properties. In one embodimentthe hydrophobic nanoparticles comprise SiO₂, and are modified bycovalently bound hydrophobic compounds. In one embodiment thenanoparticles comprise at least one silica derivative. Hydrophobicallymodified SiO₂ particles include but are not limited to particles ofsilica modified with dimethyl silylate.

The term carbon material encompasses material based on carbon. Examplesof carbon materials include but are not limited to graphite andgraphene. Particles of carbon have the advantage of improved heatconductivity compared to silica.

In one embodiment the average size of the nanoparticles is about 10 nm.In one embodiment the average size of the nanoparticles is from 1 to 50nm. In another embodiment the average size of the nanoparticles is from1 to 20 nm.

In one embodiment the hydrophobic nanoparticles are made of modifiedpyrogenic silica. In the following paragraph the manufacture of suchparticles are described. The silica (SiO₂) can be formed from SiCl₄ andH₂ in a flame at over 1000° C. This gives SiO₂ particles, primarynanoparticles in the size range about 5-50 nm. The primary nanoparticlesmay fuse together to form larger aggregates typically 100-1000 nm insize. In some embodiments the larger aggregates of nanoparticles areelongated structures. The particle size for the nanoparticles refers tothe primary nanoparticles before they aggregate into larger structures.The SiO₂ particles are modified in a gas phase with Si—O—Si bonds to theparticles. —Si—OH groups on the surface of the particles are reactedwith X—Si— groups on the modifiers, where X is a halogen atom to obtaina covalent bond between the modifier and the particle. Modifiers includebut are not limited to organochlorosilanes such as dimethylchlorosilane,polydimethylsiloxanes, hexamethyldisilazane, and long chain alkylsilanessuch as octylsilanes. This modification gives hydrophobic silicaparticles. In one embodiment the hydrophobic silica particles have1-Si—OH group per 1 nm². In an alternative embodiment the hydrophobicsilica particles have 0.5-Si—OH groups per 1 nm².

Typical physical data for the hydrophobically modified silicananoparticles manufactured as described in the previous paragraph are asfollows: BET surface area measured according to DIN EN ISO 9277/DIN66132 varies from about 90 to about 250 m²/g. pH in a 4% dispersion in a1:1 mixture of water:methanol measured according to DIN EN ISO 787-9varies from about 3.8 to about 8.0. The tamped density measuredaccording to DIN EN ISO 787/11 varies between about 40 to about 70 g/l.The weight loss during drying for 2 h at 105° C. measured according toDIN EN ISO 787-2 varies between about less than 0.5 wt % to less thanabout 1.5 wt %. The carbon content measured according to DIN EN ISO3262-20 varies from about 1.0 to about 4.5 wt %.

The NCS particles have in one embodiment an average size in the range20-100 μm, including the coating. In an alternative embodiment the NCSparticles have an average size from 5 to 500 μm. The average size of theNCS particles always includes the coating. It must be realized that theNCS particles can agglomerate to clusters comprising many NCS particles.The average particle size is measured without agglomeration of NCSparticles.

In one embodiment the particle further comprises at least one liquid. Inone embodiment the inner part of the particle comprises at least oneliquid. In one embodiment the particle further comprises water.

In a second aspect there is provided a device adapted to perform anabsorption process, said device comprising at least one particle,wherein said particle comprises an inner part and an outer coating,wherein said inner part comprises at least one selected from the groupconsisting of a salt and CaO and wherein said outer coating comprisesnanoparticles, and wherein said particle has an average size from 1 to1000 μm.

In one embodiment the device is an absorption chemical heat pump. In oneembodiment the device is an apparatus for cooling adapted to utilize anabsorption process. In one embodiment the device is a machine forgathering excess heat adapted to utilize an absorption process. In oneembodiment the device is a device for storage of energy adapted toutilize an absorption process. In one embodiment the device is a thermalsolar collector adapted to utilize an absorption process. In oneembodiment the device is a roof brick or roof cover panel for productionof cooling and heating adapted to utilize an absorption process.

There is further provided use of a particle as described above in anabsorption process. In one embodiment the absorption process is carriedout in a chemical heat pump.

In one embodiment a particle as described above is used as storage ofchemical energy. In one embodiment of the storage said inner partcomprises CaO. CaO is advantageous to use as storage of chemical energysince high temperatures can be utilized. A high temperature differenceΔT gives high efficiency.

There is further provided a method for manufacturing a particlecomprising an inner part and an outer coating, said inner partcomprising at least one selected from the group consisting of a salt andCaO and said outer coating comprising hydrophobic nanoparticles, saidmethod comprising the steps: a) mixing at least one selected from a saltand CaO with hydrophobic nanoparticles, and b) mixing with sufficientenergy to obtain particles comprising at least one selected from a saltand CaO coated with nanoparticles.

In one embodiment the at least one selected from a salt and CaO and thenanoparticles are mixed together with at least one liquid in step a). Inan alternative embodiment the salt and/or CaO is mixed with thenanoparticles without adding any liquid.

The NCS particle has several fields of use. One non limiting example isthe use in a device adapted to perform an absorption process, saiddevice comprising a salt coated with nanoparticles.

In one embodiment the particle comprise at least one liquid. In oneembodiment the liquid comprises water. In one embodiment the liquid iswater. Most of the liquid resides in the inner part of the particle. Thecoating is permeable to the liquid. Possible solvents in addition towater include but are not limited to methanol, ethanol, ammonia,methylamine, ethylamine, and liquid CO₂.

Without wishing to be bound by any particular scientific theory theinventor believe that the nanoparticles are attracted to the inner partof the particle by an attractive force (Debye force) between a dipoleand an induced dipole. The salt with or without water displays a dipole,whereas the nanoparticles possess a polarisability. Thus thenanoparticles are preferably chosen from materials that are polarisable.

The NCS particles should float if put on the surface of water. It ispossible to test manufactured NCS particles after coating by gentlyplacing NCS particles on the surface of water. It the NCS particlesfloat on the air-water surface the NCS particles are good. If the NCSparticles do not float something with the manufacturing process may bewrong, or the starting material may be unsuitable.

The NCS particle is an interesting material for many application areas,in particular for absorption processes.

With the NCS particle of the present invention, corrosion is greatlyreduced and even very corrosion sensitive materials such as aluminummight be considered for use as material for a machine working accordingto the absorption process. The reason for this is that the saltessentially stays inside the barrier of nanoparticles due to strongsurface tension; the nanoparticle coating is only permeable to the gasphase of the solvent. The salt thereby never or to a very limited extentcomes in contact with the corrosion sensitive material.

With the reduced corrosion characteristics of the NCS particle of thepresent invention, an absorption process can also be performed inatmospheric pressure as opposed to a vacuum environment. If the salt wasnot coated with the nanoparticles, the oxygen contents in theatmospheric air would decrease the lifetime of the absorption processdue to heavy corrosion. The NCS particle of the present inventiontherefore opens up many new application areas for absorption processescomprising a salt.

Moreover, in today's absorption processes, large heat exchangingsurfaces, preferably comprising a metal, are needed to create largecontact surfaces between the salt and the gas phase of the solvent aswell as to create an effective heat transport to and from the solvent.Also, moving parts in an absorption machine, such as pumps used tocreate a falling film, are used to increase the contact surfaces. Byseparating and enclosing the salt within a layer of nanoparticles, thecontact surface between the salt and the solvent in gas phase isautomatically increased. Thereby, the transfer of heat to and from thesolvent can be performed by direct contact between the salt and the gasphase of the solvent, without any additional heat exchanging surfaces.Moreover, the need for using pumps and the falling film technique isreduced or even eliminated.

By preparing a coated salt, the salt acquires new characteristics. Thenew characteristics of the NCS particle of the invention results in newapplication areas for salts in absorption processes. For example, theNCS particles can be pumped in the same way as a pure liquid or a freeflowing powder and can in other words be distributed in the same way asdistrict heating and cooling, where pure water is normally used. A noncoated salt would be impossible to apply in district heating or cooling,but the coated salt reduces corrosion in the process greatly, has 10times higher energy density than pure water and causes nocrystallization of salt particles in the pumping process. The NCSparticle can store chemically bonded energy that can be released whenand where needed, creating heating or cooling. Since the NCS particlehas a high energy density and essentially does not lose its energy overtime if stored properly, the material can be transported long distances.The NCS particle can for example be charged (heated) where there isexcess energy, e.g. industry, far away from the end user, and later betransported and discharged where energy is needed.

In contrast to conventional district heating and cooling, only 1/10 of anormal pipe diameter is needed to distribute a known amount of energywith the NCS particle compared to pure liquid water. This is because thecoated particle has 10 times the energy density compared to pure liquidwater due to the heat pumping capacity of the NCS particle. Moreover,the distribution pipes for district heating or cooling can when usingthe NCS particle of the present invention be produced in cheap plasticmaterial and do not acquire any insulation since the NCS particlematerial contains latent energy as opposed to sensible energy. Since apipe of a distribution system using NCS particles does not need to beplaced in a frost protected environment, the pipes can instead be placedin the ground in the same way as a fiber cable. No special pipes forheating or cooling are needed and since heating and cooling is not usedsimultaneously, the distribution pipe can be dimensioned only based onthe average need for heating.

Application areas for the NCS particle include but are not limited to:

Absorption chemical heat pumps for cooling and heating purposes,

Absorption chemical heat pumps working according to the hybrid principle(see for example WO 2007/139476 and WO/2009/102271) for cooling, heatingand energy storage purposes,

Machines that use absorption processes for desiccant cooling andhumidity control for good indoor climate,

Desiccant facilities and humidity control for good indoor climate,

Gathering and storing of excess heat or waste heat from for exampleindustry or vehicles to be used for heating or cooling for end userssuch as industry, hospitals, offices or private homes.

Storing gathered heat for later use.

The NCS particles may be used instead of water as an energy carrier,extending the ability in a district heating grid, to contain alsodistrict cooling. In such a grid with the present NCS particles asenergy carrier the piping could be reduced due to significantly higherenergy density compared to water.

To use the present NCS particles as energy storage or seasonal storagefor solar energy or waste heat from industry, to be used by industry,hospitals, offices, or private homes,

Cleaning or storing of hazardous exhausts gases such as methane,hydrogen, carbon dioxide, carbon oxide and other gases from combustionengines in vehicles, industry or other sources of gas emission. Allowinga subsequent regeneration of the present NCS particles when thehazardous gases are brought out of harm's way from for instance denselypopulated areas to a place where the gases safely can be taken care of,

Converting thermal solar collectors from only heating, to both heatingand cooling purposes,

Roof brick and roof cover panels can with the present NCS particlesachieve extended functionality and this building material can be usedfor production of cooling and heating to the building,

Drinking water production out of humid air by means of converted thermalsolar collectors, roof bricks and roof cover panels with the present NCSparticles,

Maintenance of exact humidity in archives, museums and other relevantplaces,

Extinction of fires, especially in electronic equipment, where thepresent NCS particles can be regenerated by humidity and used again.

A common feature for many application areas is that the NCS particle isused in an absorption process. A volatile liquid in gas phase isabsorbed by the coated salt in an exothermic reaction. When the coatedsalt containing the volatile liquid is heated, the liquid is released asa gas in an endothermic reaction.

Other features and uses of the invention and their associated advantageswill be evident to a person skilled in the art upon reading thedescription and the examples.

It is to be understood that this invention is not limited to theparticular embodiments shown here. The following examples are providedfor illustrative purposes and are not intended to limit the scope of theinvention since the scope of the present invention is limited only bythe appended claims and equivalents thereof.

EXAMPLES Example 1

In one experiment 95 parts of an aqueous solution of LiBr (32 wt %) waspoured into a blender of type OBH Nordica 1.5 L and 5 parts of ahydrophobic silica derivative was added to the salt solution. Mixing wascarried out at >10 000 rpm during three intervals, each interval lastingapproximately 30 s. The resulting material was a dry and free flowingwhite powder. The salt coated with nanoparticles was thereafter heattreated.

Example 2 Corrosion Properties of a Salt Coated with Nanoparticles onCopper, Steel and Aluminum

The salt coated with nanoparticles was prepared according to example 1above. The original LiBr content in the aqueous solution was 32 wt %.

One teaspoon of the salt coated with nanoparticles was put on threedifferent metals:

copper

steel

aluminum

The metals were heated in an atmospheric environment in an oven at 300°C. for about 1 hour.

For comparative reasons, an aqueous solution of 32 wt % LiBr was pouredon a copper sheet and heated on a heat plate for about 15 minutes (lessthan 300° C.).

Corrosion occurred rapidly on the copper sheet when the aqueous saltsolution was used. A blue/green color of oxidation products became veryclear and a hole was formed in the sheet. The copper sheet that wasexposed to the salt coated with nanoparticles did not show any signs ofcorrosion.

Neither did the metal sheets of steel and aluminum show any signs ofcorrosion when being exposed to the salt coated with nanoparticles.

Example 3 Reversibility of the Salt Coated with Nanoparticles when Usedin an Absorption Process

The salt coated with nanoparticles was prepared according to example 1above. The original LiBr content in the aqueous solution was 32 wt %. Areactor in a small scale absorption machine was filled with 50 gram ofthe salt coated with nanoparticles, the salt coated with nanoparticlesthereby containing 34 gram water. The reactor was connected to acondenser/evaporator via a gas transport channel. Thecondenser/evaporator was filled with 100 gram of water.

The absorption machine was charged by heating the reactor to 120-150° C.during 4-12 hours with a heat sink on the condenser/evaporator side ofapproximately 6° C.

The absorption machine was discharged by heating thecondenser/evaporator to 17° C. while having a heat sink of approximately25-30° C. connected to the reactor.

During charging, water evaporates from the salt coated withnanoparticles and is transported as water vapor to thecondenser/evaporator where the vapor condenses and forms pure liquidwater. The charging process can be continued until there is no waterleft in the salt coated with nanoparticles. It appears as though thesalt coated with nanoparticles does not alter its appearance or breakdown into separate salt particles and nanoparticles. Moreover, duringdischarge the “dry” salt coated with nanoparticles can again absorbwater vapor coming from the condenser/evaporator without changing itsappearance and while still being a dry powder.

Measurements of the reversibility of the salt coated with nanoparticleswere made during the absorption process described above. After charging,the reactor was weighed on an accurate scale to investigate how muchwater that had left the salt coated with nanoparticles. Afterdischarging, the reactor was weighed once more to investigate how muchwater that had returned to the salt coated with nanoparticles in thereactor. Two parallel modules where running at the same time.

The changes shown in the table below depends on variations in ambientconditions. However, over time the tests in both of the modules showthat the same or more content of water gradually returns to the reactor.The gradual increase could mean that the useable range of possibleutilization (absorbing water) of the salt coated with nanoparticles isalways well above the normal range.

Measurement Returning water to Day # the reactor (gram) 1 1 32.3 2 227.0 2 3 30.9 3 4 29.5 3 5 32.5 4 6 32.8 4 7 34.5 5 8 37.2 5 9 32.4 6 1037.1 6 11 37.4 7 12 34.5 7 13 35.8 8 14 37.0 8 15 38.7

The above results confirm the reversibility concerning absorption anddesorption of water for the salt coated with nanoparticles.

The test was also carried out with as high charging temperature as 190°C. to show stability of the salt coated with nanoparticles to hightemperatures.

Example 4 Contamination by Means of Migrations of Salt Droplets to theCondenser/Evaporator

The salt coated with nanoparticles was prepared according to example 1above. A reactor in a small scale absorption machine was filled with thesalt coated with nanoparticles. The reactor was connected to acondenser/evaporator via a gas transport channel. As a barrier betweenthe reactor and the condenser/evaporator, a filter with large enoughpores to prevent the salt coated with nanoparticles from escaping to thecondenser/evaporator was placed.

The absorption machine was charged by heating the reactor to 120-150° C.during 4-12 hours with a heat sink on the condenser/evaporator side ofapproximately 6° C.

During charging, the water evaporates from the salt coated withnanoparticles and is transported to the condenser/evaporator via the gastransport channel. In the condenser/evaporator, the water vaporcondenses to liquid water.

After charging was complete, the condenser/evaporator was opened and theliquid water was analyzed for possible salt ions to investigate if anyof the salt had been transported with the water vapor to thecondenser/evaporator.

Three liquid samples were prepared in three beakers: a) contaminatedwater—a sample from a prior art machine; b) condenser/evaporator waterfrom a machine with salt coated with nanoparticles; c) distilledwater—reference. The presence of salt traces (lithium bromide in thepresent example) can be determined by means of a silver nitrate reagent.The silver nitrate forms a non soluble silver bromide that develops as amilky/opaque color. LiBr+AgNO₃→AgBr↓+LiNO₃

The silver nitrate reagent was added to all three beakers. Case a)revealed the presence of bromide ions in the liquid. The cases b) and c)revealed the absence of bromide ions in the liquid, i.e. the water fromthe condenser/evaporator of the present example was completely pure andclean from any salt ions, i.e. the salt stays inside the network ofnanoparticles in the NCS particle.

Migration of micro droplets of salt solution inside the machine canthereby be stopped by using the NCS material, due the binding forces ofthe salt inside the salt coated with nanoparticles.

Example 5 Open Channels for Gas Penetration

Open channels ensure the gas access for interaction with the salt coatedwith nanoparticles. The size of the channels remains the same and doesnot change with time. Large contact surface (700-1000 cm²/cm³) ensureseffective interaction between the salt coated with nanoparticlesmaterial and gas.

Example 6

Four different types of NCS particles were prepared from LiCl,Na₂S*9H₂O, CaO, and LiBr respectively. The nanoparticles were silicaparticles with polydimethylsiloxy-groups covalently bound to thesurface.

For the nanoparticles the BET surface area measured according to DIN ENISO 9277/DIN 66132 was about 120 m²/g. pH in a 4% dispersion in a 1:1mixture of water:methanol measured according to DIN EN ISO 787-9 variedfrom about 4.0 to about 6.0. The tamped density measured according toDIN EN ISO 787/11 was about 50 g/l. The weight loss on drying for 2 h at105° C. measured according to DIN EN ISO 787-2 was less than about 0.6wt %. The carbon content measured according to DIN EN ISO 3262-20 wasabout 4.5 wt %.

The salt and the nanoparticles were mixed in a blender of type OBHNordica 1.5 L. Mixing was carried out at >10 000 rpm during threeintervals, each interval lasting approximately 30 s. The resultingmaterial was a uniform free flowing powder that did not get wetted inwater.

Example 7

In one experiment 98 parts of solid CaO was placed into a blender oftype OBH Nordica 1.5 L and 2 parts of a hydrophobic silica derivativewas added as well. Mixing was carried out at >10 000 rpm during oneinterval of approximately 30 s. The resulting material was a dry andfree flowing slightly gray powder.

For the nanoparticles the BET surface area measured according to DIN ENISO 9277/DIN 66132 was about 120 m2/g. pH in a 4% dispersion in a 1:1mixture of water:methanol measured according to DIN EN ISO 787-9 variedfrom about 4.0 to about 6.0. The tamped density measured according toDIN EN ISO 787/11 was about 50 g/l. The weight loss on drying for 2 h at105° C. measured according to DIN EN ISO 787-2 was less than about 0.6wt %. The carbon content measured according to DIN EN ISO 3262-20 wasabout 4.5 wt %.

Example 8

In one experiment 93 parts of an aqueous solution of LiCl (40 wt %) waspoured into a blender of type OBH Nordica 1.5 L and 7 parts of ahydrophobic silica derivative was added to the salt solution. Mixing wascarried out at >10 000 rpm during two intervals, each interval lastingapproximately 30 s. The resulting material was a dry and free flowingwhite powder. The salt coated with nanoparticles was thereafter heattreated.

For the nanoparticles the BET surface area measured according to DIN ENISO 9277/DIN 66132 was about 120 m2/g. pH in a 4% dispersion in a 1:1mixture of water:methanol measured according to DIN EN ISO 787-9 variedfrom about 6.5 to about 8.0. The tamped density measured according toDIN EN ISO 787/11 was about 200 g/l. The weight loss on drying for 2 hat 105° C. measured according to DIN EN ISO 787-2 was less than about0.6 wt %. The carbon content measured according to DIN EN ISO 3262-20was about 2.8 wt %.

Example 9 Particle Stability of the CaO Coated with Nanoparticles whenUsed in an Absorption Process

The CaO coated with nanoparticles was prepared according to example 7above. A reactor made of small copper dish in a small scale absorptionmachine made of glass was filled with 0.4 gram of the CaO coated withnanoparticles. The reactor was connected to a condenser/evaporator via agas transport channel. The condenser/evaporator was filled with 0.5 gramof water.

The absorption tube was charged by heating the reactor to 370-400° C.during 1 minute with an induction heater. A heat sink on thecondenser/evaporator side is an ambient air of approximately 21° C.

The absorption machine was discharged during 3 minutes by shutting offthe induction heater. The condenser/evaporator was kept at roomtemperature approximately to 21° C. during the discharge.

During charging, calcium hydroxide coated with nanoparticles decomposesinto CaO coated with nanoparticles and water that evaporates and istransported as vapor to the condenser/evaporator side of a glass tubewhere the vapor condenses and forms pure liquid water. It appears asthough the CaO coated with nanoparticles does not alter its appearanceor break down into separate oxide particles and nanoparticles. Moreover,during discharge the “dry” CaO coated with nanoparticles can againabsorb water vapor coming from the condenser/evaporator without changingits appearance and while still being a dry powder.

Study of the stability of the CaO coated with nanoparticles was madeduring the absorption process described above. The electron microscopepictures of CaO/Ca(OH)2 coated with nanoparticles were made after 1300charge/discharge cycles and compared with electron microscope picturesof un-cycled CaO/Ca(OH)2 coated with nanoparticles. The un-cycledCaO/Ca(OH)2 coated with nanoparticles and X10000 SEM picture is shown onFIG. 3 and after 1300 cycles on FIG. 4. The structure of CaO/Ca(OH)2coated with nanoparticles remains the same.

Example 10 Reversibility of the CaO Coated with Nanoparticles when Usedin an Absorption Process

The CaO coated with nanoparticles was prepared according to example 7above. An absorption machine was built and consisting of a reactor tubeand a condenser/evaporator one. A reactor made of steel tube with 70 mminner diameter and equipped with a steam channel of 40 mm diameter madeof copper mesh. The reactor contains 300 grams of CaO coated withnanoparticles placed between the rector tube wall and the steam channel.The reactor was connected to a condenser/evaporator via a gas transportchannel equipped with a pressure gauge and a vacuum pump connection. Thecondenser/evaporator was filled with 250 grams of water. Thecharge/discharge process is carried out in vacuum. The pressure iscontrolled by a pressure gauge.

The absorption tube was charged by heating the reactor to 470° C. during12 hours in an oven. A heat sink on the condenser/evaporator side is anambient air of approximately 21° C.

The absorption machine was discharged during 3 hours. Thecondenser/evaporator temperature was kept between 60-70° C. The reactortemperature rise was registered continuously with temperature sensor.The condenser/evaporator mass change was measured during dischargecycle.

30 cycles have been performed according to 110-111. Thecondenser/evaporator mass change made up 96.0-97.0 grams every cycle.The peak reactor temperature varied between 380-420° C. when the reactorstart temperature (at the beginning of discharge) varied between270-320° C. Therefore no degradation in performance has been measured.

The reactor tube was open after 27 cycles in order to inspect thequality of the powder consisting of CaO coated with nanoparticles. Thepowder possesses the same color as at the start and does not include“hard” agglomerates.

Example 11

In one experiment 90 parts of solid CaO was placed into a blender oftype OBH Nordica 1.5 L and 10 parts of a nanoparticles of graphite oftype MKN-CG-400 MK Impex Corp. Mixing was carried out at >10 000 rpmduring two intervals of approximately 30 s. The resulting material was adry and free flowing ash-like powder.

1. A particle comprising an inner part and an outer coating, said innerpart comprises at least one selected from the group consisting of a saltand CaO and said outer coating comprises hydrophobic nanoparticles,wherein the particle has an average size from 1 to 1000 μm.
 2. Theparticle according to claim 1, wherein said salt is hygroscopic.
 3. Theparticle according to claim 1, wherein said salt is selected from thegroup consisting of chlorides, chlorates, perchlorates, bromides,iodides, carbonates and nitrates of lithium, magnesium, calcium,strontium, barium, cobalt, nickel, iron, zinc, manganese, potassium, andaluminum as well as sulphides and hydroxides of lithium, sodium andpotassium.
 4. The particle according to claim 1, wherein said salt isselected from the group consisting of Na₂S, LiBr, LiCl, CaCl₂, andCaBr₂.
 5. The particle according to claim 1, wherein said nanoparticlescomprise at least one material selected from the group consisting ofhydrophobically modified SiO₂ particles and carbon materials.
 6. Theparticle according to claim 1, wherein said hydrophobic nanoparticlescomprise SiO₂, and are modified by covalently bound hydrophobiccompounds.
 7. The particle according to claim 1, wherein said particlefurther comprises at least one liquid.
 8. The particle according toclaim 1, wherein said particle further comprises water.
 9. A deviceadapted to perform an absorption process, said device comprising atleast one particle, wherein said particle comprises an inner part and anouter coating, wherein said inner part comprises at least one selectedfrom the group consisting of a salt and CaO and wherein said outercoating comprises hydrophobic nanoparticles, and wherein said particlehas an average size from 1 to 1000 μm.
 10. The device according to claim9, wherein said salt is hygroscopic.
 11. The device according to claim9, wherein said salt is at least one salt selected from the groupconsisting of chlorides, chlorates, perchlorates, bromides, iodides,carbonates, and nitrates of lithium, magnesium, calcium, strontium,barium, cobalt, nickel, iron, zinc, manganese, potassium, and aluminum,as well as sulphides and hydroxides of lithium, sodium and potassium.12. The device according to claim 9, wherein said salt is selected fromthe group consisting of Na₂S, LiBr, LiCl, CaCl₂, and CaBr₂.
 13. Thedevice according to claim 9, wherein said nanoparticles comprise atleast one material selected from the group consisting of hydrophobicallymodified SiO₂ particles and carbon materials.
 14. The particle accordingto claim 9, wherein said hydrophobic nanoparticles comprise SiO₂, andare modified by covalently bound hydrophobic compounds.
 15. The deviceaccording to claim 9, wherein said particle further comprises at leastone liquid.
 16. The device according to claim 9, wherein said particlefurther comprises water.
 17. The device according to claim 9, whereinsaid device is an absorption chemical heat pump.
 18. The deviceaccording to claim 9, wherein said device is an apparatus for coolingadapted to utilize an absorption process.
 19. The device according toclaim 9, wherein said device is a machine for gathering excess heatadapted to utilize an absorption process.
 20. The device according toclaim 9, wherein said device is a device for storage of energy adaptedto utilize an absorption process.
 21. The device according to claim 9,wherein said device is a thermal solar collector adapted to utilize anabsorption process.
 22. The device according to claim 9, wherein saiddevice is a roof brick or roof cover panel for production of cooling andheating adapted to utilize an absorption process.
 23. An absorptionprocess, comprising contacting a particle according to claim 1 with aliquid or gas.
 24. The process according to claim 23, wherein saidabsorption process is carried out in a chemical heat pump.
 25. A processfor storage of chemical energy, comprising contacting a particleaccording to claim 1 with a liquid or gas.
 26. The process according toclaim 25, wherein said inner part comprises CaO.
 27. Method formanufacturing a particle comprising an inner part and an outer coating,said inner part comprising at least one selected from the groupconsisting of a salt and CaO and said outer coating comprisinghydrophobic nanoparticles, said method comprising the steps: a) mixingat least one selected from a salt and CaO with hydrophobicnanoparticles, and b) mixing with sufficient energy to obtain particlescomprising at least one selected from a salt and CaO coated withnanoparticles.
 28. The method according to claim 27, wherein the atleast one selected from a salt and CaO and the nanoparticles are mixedtogether with at least one liquid in step a).
 29. The method accordingto claim 28, wherein said liquid is water.